/*css reset 什么是css reset?为什么要cssreset?*/
*, h1, h2, h3, h4, h5, h6 {
    font-weight: normal;
    margin: 0;
    padding: 0;
    outline: none;
    box-sizing: border-box;
}
h1{
    color:green;
}
body{
    padding: 20px;
}
